EFO OTAR Slim: remove therapeutic_area subset from pancreas disease

[dhimmel]

I noticed EFO:0009605 (pancreas disease) is considered a therapeutic_area via <oboInOwl:inSubset>. This is the only EFO OTAR Slim therapeutic area that is not a root node (it's beneath gastrointestinal disease and endocrine system disease), so I'm skeptical it should be considered a therapeutic area. Possible background in https://github.com/EBISPOT/efo/issues/487.

To reproduce (currently based on v3.60.0):

curl --silent --location https://github.com/EBISPOT/efo/releases/download/v3.60.0/efo_otar_slim.owl | grep "EFO:0009605" --context=30

Then will see the lines:

        <oboInOwl:id>EFO:0009605</oboInOwl:id>
        <oboInOwl:inSubset>therapeutic_area</oboInOwl:inSubset>

[dhimmel]

If this is indeed a bug, perhaps it makes sense to add a test that all TAs are roots in EFO Otar Slim?